Question: Are US Patent images protected by copyright?
Answer: No with exceptions. So, yes you can use US patent drawings and text for your own purposes in most cases.
The text and the drawing of a patent are not subject to copyright restrictions except a drawing may incorporate a copyrighted or trademarked work. The copyrighted or trademarked portion should be so marked. Also design patents have similarities to copyright restrictions, but only last 14 years. If the patent “number” begins with “D”, then it is a design patent.
So a good source of drawings for blog posts or other needs is patents. See my blog post on free patent searching.
Also note, you can use materials created by the United States government without copyright restrictions. However if you don’t credit that a portion of your work consists of work of the U.S. Government, you may lose copyright protection on your entire work.